40 8 BOTANICAL GAZETTE [DECEMBER 



It is also worthy of note that in the southeastern part of this 

 region the bog flora is increased in variety by a large number of 

 plants whose range is more southerly than that of the typical 

 bog plants. Among these are Vaccinum corymbosum, V. 

 atrococcum, Rhodora canadensis, Aronia arbutifolia, and Vibur- 

 num cassinoides. Their distribution points to a northward migra- 

 tion from the southern Appalachians. 10 



VARIATIONS OF THE BOG FLORA IN GEOGRAPHIC RANGE. 



But the map has a still greater significance. The dark area 

 represents the region in which most of these plants attain their 

 highest physical development. Those who have seen the mag- 

 nificent groves of tamarack in the north, attaining a height of 

 thirty meters and a bole diameter of a meter, will appreciate 

 this fact when they compare them with the stunted groups of 

 the larch in the bogs near the southern and northern limits. 



Again, within this same belt, at least eight of the plants, the 

 buckbean, cranberry, snowberry, rosemary, leather leaf, labrador 

 tea, birch, and tamarack, are not confined to bog areas. They 

 may be said to have there a wider life-range and are to be found in 

 a variety of habitats. The tamarack, for example, is found on 

 the hills and along most of the streams. With the black and 

 and white spruce and pine, it makes up a large part of the forest. 

 Here too the buckbean, leather leaf, Labrador tea, and birch 

 occur along slow streams, and the rosemary, snowberry, and 

 cranberry in moist ravines and rich woods. 



Just as striking, perhaps, is the fact that as we go in any 

 direction away from this optimum region, the first plants to 

 diminish in size and frequency of occurrence are the arborescent 

 tamarack and birch. Then follow in close succession the shrubby 

 forms, and finally the herbaceous species." This is practically 

 a reversal of the order of their coming into a new area, and, as 

 we shall see later on, this may have some connection with the 



10 ADAMS, C. C., Southeastern United States as a center of geographical distri- 

 bution of flora and fauna. Biol. Bull. 3: 123. 1903. 



11 Scheuchzeria palustris is an exception, so far as its eastern distribution is con- 

 cerned, and has about the same range as Betula fumila, but in the west it reaches 

 its southern limit in Colorado and California. 



